DS21S07AS

Overview

The DS21S07AS is a monolithic SCSI terminator compliant with SCSI-1, Fast SCSI, and Ultra SCSI standards. It integrates a low-dropout voltage regulator and nine laser-trimmed 110Ω termination resistors with 2% tolerance. The device operates on a TERMPWR supply ranging from 4.0V to 5.5V, consuming approximately 2.5mA in the active state and 150µA in power-down mode. It features a 16-pin SOIC package and supports actively negated signals by sinking at least 200mA. The internal bandgap reference produces a precise 2.85V level for signal termination.

Feature Summary

• Provides active termination for nine signal lines with intrinsic TERMPWR decoupling
• Integrates a low-dropout voltage regulator and bandgap reference circuitry
• Supports hot-plug operations through an active-low power-down isolation mode
• Includes on-board thermal shutdown circuitry for protection

Applications

• Termination for single-ended drivers and receivers in SCSI systems
• Disk drive interface circuits requiring active termination
• RAID system components acting as targets on a SCSI bus

Procurement Notes

Verify component authenticity against official Analog Devices or Maxim Integrated documentation. Confirm the specific suffix 'AS' corresponds to the 16-pin SOIC package variant. Check for lead-free status if '+', as standard versions may not meet current environmental regulations. Ensure compatibility with existing board layouts regarding the 16-SOIC footprint and pin assignments before procurement.

Selection Notes

Select this component when designing systems requiring compliance with SCSI-1, Fast SCSI, or Ultra SCSI standards using single-ended signaling. It is suitable for applications needing reduced quiescent current and enhanced noise immunity compared to passive terminators. Consider the 16-pin SOIC package constraints and ensure adequate thermal management within the 0°C to +70°C operating range.

Part Context

The DS21S07AS belongs to the DS21S07A family of SCSI terminators manufactured by Analog Devices Inc./Maxim Integrated. It serves as a backward-compatible replacement for earlier models like the DS2107 and DS2107A. The 'AS' designation specifically identifies the 16-pin Plastic SO package version, distinct from the 20-pin TSSOP variant (DS21S07AE).

Replacement Considerations

The datasheet explicitly states backward compatibility with the DS2107 and DS2107A. Designers replacing these legacy components should verify that the new active termination requirements align with the system's power budget and signal integrity needs.